A before-and-after look of a cross-drilled component that machinists honed to remove burrs with Brush Research Mfg. (BRM) equipment.

Removing burrs and sharp edges in cross-drilled holes and other difficult-to-access areas such as undercuts, grooves, slots, or internal holes can be tedious and time consuming. Deburring the intersection of cross-drilled holes frequently found in aerospace engine components is particularly challenging.

In many applications, cross-drilled holes act as conduits for fluids, lubricants, and gases, and failure to remove burrs can cause blockage of these critical passages or create turbulence in the flow. Burrs can also lead to part misalignments, affect dimensional tolerances, and limit the overall efficiency of machined components.

“Getting rid of burrs is really important because if there is any loose material that gets dislodged when the product is in use, it can cause major problems,” says Anthony Scott, lead machinist at Orange Vise Co. in Placentia, California, a manufacturer of machine vises and quick-change fixturing components used in aerospace manufacturing.

Automating processes

The majority of techniques for deburring internal passages at cross-holes require sending parts out for processing or investing in equipment to complete the work in-house. Methods such as thermal, abrasive flow, electrochemical, and high-pressure water effectively remove excess material, but they also build time into the manufacturing process and add cost.

A better option, however, is to integrate deburring into the automated process with a crosshole-deburring tool such as the Flex-Hone from Brush Research Mfg. (BRM). Operators can speed manufacturing and ensure uniform quality for precision parts.

According to Scott, flexible hones cost-effectively smooth edges and produce a blended radius for crosshole deburring.

“It is really about accessibility, because there aren’t really any other tools that can do what a Flex-Hone can,” Scott says. “Whether it is internal grooves or multiple cross-holes, there is really no way to reach those areas with any other tool.”

The ball-style hone is a highly specialized abrasive tool instantly recognizable by its appearance. Characterized by the small, abrasive globules permanently mounted to flexible filaments, it is a flexible, low-cost tool for sophisticated surfacing, deburring, and edge-blending.

Available in sizes ranging from 0.16" (4mm) diameter hones to those up to 36" (914mm) or more in diameter, tools can be custom designed to size, shape, and abrasive grit to fit the application.

Honing irregular workpieces

“I used the Flex-Hone quite a bit when I was working in aerospace,” explains Ken Spaulding of Zodiac Engineering, a contract manufacturer in California. “We did a lot of parts that involved tubes with multiple crossholes and slots. Getting inside to reach the burrs, particularly if the walls are thick, is extremely difficult.”

With a background in aerospace parts as well as moldmaking, Spaulding is currently focused on creating products of his own design, while continuing to perform contract manufacturing work.

Spaulding appreciates how the flexible hone’s abrasive globules each have independent suspensions that are self-centering, self-aligning to the bore, and self-compensating for wear, all facilitating close-tolerance finishing work.

“The hone conforms to whatever you are working with, even if it’s irregular,” Spaulding says. “For example, if the back side of the part is not flat or not on a consistent level plane in Z, the tool is flexible enough to still remove any burrs.”

The deburring tool is typically rotated into the main bore where crossholes break. After a few clockwise strokes, the tool is removed and the spindle reversed to rotate and stroke the flexible hone in a counter-clockwise direction for a few more strokes. The forward and reverse rotation creates a symmetrical deburring pattern. Coolant should be used to keep metal cuttings and deburred metal in suspension.

Customized tooling

According to Orange Vise’s Scott, although the Flex-Hone is often used with automated production equipment it can also be used for secondary deburring options off-line as needed.

“The tool can be used in CNC machines and also with a cordless drill,” Scott says. “So, if you manage to deburr 90% of the holes in a machine, but have a few left you can’t access easily, you can use it with a handheld drill and maintain the uniformity in surface finish and process.”

Brush Research Mfg.